Photographic process and materials used therein

ABSTRACT

A method of and material for recording information using a recording material having a water-permeable recording layer consisting essentially in one embodiment of a continuous phase of film-forming hydrophilic colloid binder having uniformly distributed therethrough finely divided particles of a hydrophobic oil, wax, or thermoplastic polymer, together with finely divided particles of an inorganic photoconductive compound, and in another embodiment of a continuous phase of a film-forming hydrophilic colloid binder having uniformly distributed therethrough finely divided particles of a hydrophobic oil, wax, or thermoplastic polymer, together with a water-soluble organic photoconductive dye, wherein such recording layer is imagewise exposed to active electromagnetic radiation to render the exposed areas substantially impermeable to water, while the unexposed areas remain permeable but without significantly increasing the temperature of such layer and is thereafter developed by contacting the same with an aqueous liquid to produce a visible change by penetration or removal of the unexposed regions of the layer by such liquid. The binder should be present in a ratio of about 1:1 to 1:10 relative to the hydrophobic particles, while the photoconductor is present in a ratio of 1:3 to 5:3 in the case of an inorganic photoconductor and at least about 0.05 percent by weight in the case of the organic photoconductive dye, both relative to the hydrophobic particles.

United States Patent Vrancken 5] Feb. 15,1972

[54] PHOTOGRAPHIC PROCESS AND MATERIALS USED THEREIN [72] Inventor: Marcel Nicolas Vrancken, Hove, Belgium [73] Assignee: Gevaert-Agt'a N.V., Mortsel, Belgium [22] Filed: Apr. 24, 1969 [21] Appl. No.: 819,086

[30] Foreign Application Priority Data Apr. 24, 1968 Great Britain ..l9,457/68 [52] US. Cl. ..96/48, 96/1 R, 96/ 1.5, 96/1.8, 96/27 R, 96/35, 250/65 [51] Int. Cl ..G03c 5/24 [58] Field ofSearch ..96/1,1.5, l.8,33,27,35, 96/48 PD; 250/65 [56] References Cited UNITED STATES PATENTS 3,514,597 5/1970 Del-laes et al .250/65 Steppan et al. Vrancken Hoshino et al.. Michalchik ..96/1

Primary Examiner-George F. Lesmes Assistant Examiner-J. P. Brammer Attorney-William J. Daniel [57] ABSTRACT A method of and material for recording information using a recording material having a water-permeable recording layer consisting essentially in one embodiment of a continuous phase of film-forming hydrophilic colloid binder having uniformly distributed therethrough finely divided particles of a hydrophobic oil, wax, or thermoplastic polymer, together with finely divided particles of an inorganic photoconductive compound, and in another embodiment of a continuous phase of a film-forming hydrophilic colloid binder having uniformly distributed therethrough finely divided particles of a hydrophobic oil, wax, or thermoplastic polymer, together with a water-soluble organic photoconductive dye, wherein such recording layer is imagewise exposed to active electromagnetic radiation to render the exposed areas substantially impermeable to water, while the unexposed areas remain permeable but without significantly increasing the temperature of such layer and is thereafter developed by contacting the same with an aqueous liquid to produce a visible change by penetration or removal of the unexposed regions of the layer by such liquid. The binder should be present in a ratio of about 1:1 to 1:10 relative to the hydrophobic particles, while the photoconductor is present in a ratio of 1:3 to 5:3 in the case of an inorganic photoconductor and at least about 0.05 percent by weight in the case of the organic photoconductive dye, both relative to the hydrophobic particles.

17 Claims, No Drawings PHOTOGRAPHIC PROCESS AND MATERIALS USED THEREIN The present invention relates to photographic recording and reproduction of information and to recording and reproduction materials suited therefor.

More particularly this invention relates to a process for producing an irreversible change in physical behavior in the areas where a photosensitive material is subjected to a sufficient degree of electromagnetic radiation. The photosensitive element, which will be described more in detail hereinafter, by the action of active electromagnetic radiation undergoes a decrease of permeability and removability by water. This means that in said element an image or signal in the form of electromagnetic radiation is recorded as a pattern of differences in permeability for and removability by water.

It is one of the objects of the present invention to produce photographic copies of line work, halftone and continuous tone originals by means of a simple aqueous processing.

It is another object of the present invention to produce polymer patterns which make part of a printing master, e.g., a planographic printing master, and a screen printing master such as a stencil.

Other objects will become apparent of the description and examples which are not limiting the invention to the embodiments covered thereby.

The present invention resides in a method for recording respectively reproducing information, which method comprises (l) informationwise exposing to active electromagnetic radiation a recording material comprising at least one waterpermeable recording layer essentially consisting of one or more photoconductive compounds and dispersed finely divided material comprising hydrophobic particles consisting of or comprising a hydrophobic substance, said photoconductive compounds and dispersed hydrophobic particles being present in the recording layer in such an amount that without a substantial informationwise increase of the temperature of the recording layer, the latter undergoes a reduction in waterpermeability in the sufficiently irradiated portions, and (2) developing the so formed latent image by penetration of a liquid into the nonirradiated or insufficiently irradiated portions of the recording layer bringing about a visible change in correspondence in these portions, or by removal of the nonirradiated or insufficiently irradiated portions of the recording layer.

The dispersed hydrophobic particles should be for the most part in very near relationship (only separate from each other over a very small distance) in order that neighboring particles in any given area of the recording layer can coagulate when the layer in that area, which is sensitive to electromagnetic radiation, is sufficiently irradiated.

A preferred recording material for use according to the present invention consists of or incorporates a water-permeable recording layer or sheet containing finely divided hydrophobic substance dispersed in a hydrophobic binder, preferably in a ratio by weight of at least l:l, said recording material further containing in working relationship to said dispersed hydrophobic substance a substance the electrical resistivity of which decreases on exposure to electromagnetic radiation.

With a proper amount of hydrophilic binder it is even possible to use liquid and semisolid hydrophobic dispersed material, e.g., nonpolar organic liquids or soft substances such as paraffinic oil, soft hydrophobic compounds of aromatic nature, e.g., pyrene and hydrophobic waxes.

The finely divided hydrophobic substance is preferably composed wholly or mainly of hydrophobic thermoplastic substance, and this substance is preferably solid at room temperature (softens preferably between 30 and 200 C.). The recording layer preferably contains solid hydrophobic particles dispersed in a hydrophilic binder in a ratio by weight of at least 1:1, and such particles preferably consist wholly or mainly of hydrophobic thermoplastic material, e.g., hydrophobic thermoplastic polymeric material.

The hydrophobic substance is preferably applied from an aqueous dispersion wherein a dispersing agent is used for dispersing the finely divided hydrophobic material and for keeping it in dispersed state. The hydrophobic material may be chemically treated to make it more easily dispersible in an aqueous medium. Such is e.g., the case by partial oxidation of polyethylene.

Substances the electrical resistivity of which one exposure to electromagnetic radiation decreases are, e.g., inorganic and organic photoconductive semiconductive compounds. The photoconductive substances which can be applied in the present invention may be N-type as well as Ptype semiconductors or combinations of both types.

A change of the conductivity possibly also charging capacity, electron-accepting or electron-emission power, in other words a change of the potential level of the photoconductive particles in respect of the dispersed material in the surrounding medium is assumed as being the cause that a coagulation of the said dispersed hydrophobic particles takes place. This assumption is based on the knowledge that theoretically flocculation and coagulation are the same phenomena. Indeed, in a suspended solid system both phenomena are characterized by interparticular surface reactions annihilating or decreasing the repelling forces between separate dispersed particles (ref. Ind.Eng.Chem., C. P. Priesing Vol. 54, No. 8, 1962, p. 38-45, A theory of Coagulation useful for Design").

Stability of colloidal particles in aqueous dispersions is attributed to hydration and electrostatic charge. The dispersed particles present to the dispersing medium an electronic or electrostatic capacity, which means that they can lose, gain or share electrons by forming bonds such as ionic, covalent, hydrogen, dipolar, or induced dipolar bonds. These bonds can be classified in terms of bond energies (given as kilocalories per mole). Ionic crystal bonds are the strongestviz, more than to 200, covalent bonds about 50 to 100, hydrogen bonds 1 to 10, and dipolar bonds less than 5. Similar to dipolar bonds are bonds being the result of induced polarization (London-van der Waals forces) in molecules and atoms, which normally are electrically neutral. Such bonds are also of low energy. In most coagulation processes, covalent bonds or ordered ionic crystal lattices are neither made nor broken, although the system is subject to ionic equilibrium in solution.

The electrical capacity formed around a hydrophobic or lyophobic dispersed particle is built up by the electrical double layer surrounding the particle. A fixed layer of electrostatic charges, e.g., of ions surrounds the dispersed particle, which may originate from within the colloidal mass itself, or may be formed thereon by a preferential adsorption thereto of a dispersing agent.

In flocculation four forces act on both the dispersed phase and the coagulant, viz, Brownian motion, gravity coulombic charge and agitation.

Colloidal stability depends on several parameters, the most important being the water-adsorbing character of substances, valence and concentration of ions surrounding the dispersed particle having an electrical double layer. It is assumed that at least one of said parameters is changed by the exposure of the photoconductive compounds present in working relationship with the dispersed material, and that a discharge or reduction of charge present in the double layer, and consequently coagulation resulting in the direct contacting of the hydrophobic surfaces of the dispersed hydrophobic particles takes place. Note that the dispersed hydrophobic particles itself may be photoconductive or contain a photoconductor e.g., a ionoid photoconductor.

The direct contact of the hydrophobic polymer particles with each other decreases the penneability for water of the recording layer, since hydrophobic surfaces stand then in direct contact with each other without a separating hydrophilic hydration layer.

The binding forces between the directly contacting hydrophobic particles are adhesion forces. The adhesion of the coagulated hydrophobic particles may be compared with the attractive forces that exist between polymer molecule chains. It is possible to control said adhesion by choosing as hydrophobic dispersed particles hydrophobic polymer particles of same or different chemical structure, whereby the possibility is left to create physical and chemical bonds of more or less firmity between the coagulated particles.

So, a mixture of polymer particles can be used wherein at least a part of the polymer particles contains polymer chains having groups differing in polarity and/or polarizability whereby intermolecular forces of quantum mechanic structuree.g., charge transfer complexes, can be formed. Polymers having groups with different electron-donating or electron-attracting power are, e.g., polyacrylonitrile, polyvinyl chloride, polyethylene polymethyl methacrylate, and vinyl polymers having a nucleus with aromatic character, e.g., polystyrene, polyvinyl-naphthalene, polyvinyl-anthracene, or poly-N-vinyl-carbazole, and nitro-, cyanoand halogen derivatives of the vinyl polymers having a nucleus with aromatic character.

Having stated in general the cgncepts of this invention and having given a probable explanation of the working mechanism laying on the basis of the water-permeability-impermeability differentiation in the recording element by active imagewise or recordwise electromagnetic radiation, we will give now a more detailed description of the composition and structure of various photosensitive elements, which form or make part of recording and reproduction materiaTs suited for being used according to the present invention.

According to a preferred embodiment the photosensitive element contains hydrophobic thermoplastic polymer particles having a softening point high enough to not coalesce on being coated at 30 C. Said hydrophobic thermoplastic polymer particles are dispersed in a hydrophilic binding agent (in an amount not preventing a substantial reduction in water permeability of the coating on exposure). Said hydrophobic thermoplastic polymer particles stand in working relationship i.e., in effective contact with (a) photosensitive substance(s) that on exposure with active electromagnetic radiation cause(s) coagulation of the dispersed polymer particles.

Whether a photosensitive substance is suited for that purpose or not can be readily determined by a routine experimentation with a mixture of thermoplastic hydrophobic resin particles dispersed together with the photosensitive substance in a hydrophilic binder, the volume of binder being preferably not higher than that of the resin particles.

By the tenn active electromagnetic radiation is understood that type and degree of radiation effecting the desired reduction of permeability for water of the recording layer without a substantial rise in temperature. In case dispersed thermoplastic hydrophobic substances being solid at room temperature C.) are used, the temperature should not rise above the softening point of the hydrophobic thermoplastic particles.

By the term effective contact" is understood that the photoconductive substance(s) is (are) so intimately associated (mixed) with the dispersed hydrophobic material (which itself may be photoconductive) that a reduction in water permeability of the recording layer can take place under the described exposure conditions in the sensitivity range of the applied nonspectrally or spectrally sensitized photoconductive substance.

An information-recording process, wherein a water-permeable recording layer is used, at least the greater part by weight of which is formed by a dispersion of particles composed wholly or mainly of hydrophobic thermoplastic polymeric material, solid at room temperature, in a hydrophilic binder,

the weight ratio of said polymer particles to said binder being in excess of 1:1, and said layer having been fonned by forming and drying a layer comprising said particles in an aqueous medium containing the binding agent, and being capable of being rendered water-impermeable or less water-permeable in any given area of the layer by the action of heat and/or pressure at that area, and wherein such layer is information-wise heated and/or subjected to pressure to such an extent that the information is recorded in terms of a difference in the water permeabilities of different areas of said recording layer, and parts of said recording layer which remain water-permeable are removed, is described in the Canadian Pat. No. 787,843 of Gevaert Photo-Producten N.V., issued June 18, 1968.

Preferred hydrophobic thermoplastic polymers which are solid at room temperature and are applied in latex form are polyethylene and polyvinylidene chloride having a melting point of 110 and 190 C. respectively, and the following polymers with their respective glass transition temperatures: polystyrene C,), polymethyl methacrylate (comprised between 70 and C.), polyethyl methacrylate (50 C.), polyvinyl chloride (near 70 C.), polyacrylonitrile (near 100 C. and poly-N-vinylcarbazole (200 C.

As is known, the glass transition temperature can be lowered by the addition of some substances called plasticizers, and by copolymerization.

The molecular weight of the polymers usable in the process of the present invention may vary within wide limits. Polymers possessing a molecular weight between 5,000 and 1 million are preferred. With polyethylene having a molecular weight of between 15,000 and 50,000 especially good results were obtained. Of course, mixed dispersion of polymer particles are considered too and the different polymer particles may contain ingredients, e.g., those which impart to the polymer particles a color or opacity.

The aqueous dispersion of the polymers (homopolymers or copolymers) is preferably prepared by polymerization in emulsion of one of more polymerizable monomers according to known techniques, e.g., those described by W. Sorenson and T. W. Campbell, Preparative Methods of Polymer Chemistry, Interscience Publishers, New York (1961). In the emulsion polymerization use is made of dispersing agents such as those described by K. Laux, Die Grenzflachenaktiven Stoffe in Winnacker-Kiichlers Chemische Technologie" Carl l-lanser-Verlag Munich (1960) p. -242.

Further polymer dispersions which are appropriate for being applied in the present invention can be obtained by dispersing in water mechanically finely divided polymer particles preparably with the help of surfactants and/or optionally with hydrophilic protective colloids such as polyvinyl alcohol and gelatin. A preferred latex of that type contains polyethylene particles. Excellent results are obtained with latexes prepared by emulsion polymerization. In this polymerization technique the monomer is dispersed by stirring in very fine droplets in the presence of water, emulsifyers (soaps, ammonium oleate, sulfonated fatty alcohols and the like), protective colloids (carboxymethyl cellulose, polyvinyl alcohol and the like), e.g., a buffering system, a surfactant and a water-soluble catalyst, e.g., hydrogen peroxide or a persulphate. The polymer is obtained as a stable dispersion of polymer particles in water. In that case the electrical double layer is built up by the dispersing agent.

The dispersed polymer particles may size from 0.01p. to 50 u. However, the larger the particles, the less the resolving power on recording. Very good results are obtained with dispersions the polymer particles of which size from 0.05to

2n. Dispersions wherein the dispersed particles size from 1 ,u to 1 mp, are considered as colloidal systems. A colloidal system the continuous phase of which is formed by water (dispersing medium) and the dispersed phase is formed by particles sizing from 1 ,u. to 0001p, is called a hydrosol. Good results are obtained when using such hydrosols the polymer particles of which are not greater than 0.1 Good results are further obtained when in the recording layer an amount of polymer is used comprised between 0.5 g. and 10 g./sq.m. The thickness of recording layers according to the present invention preferably varies between 0.5; and 10 p" The support and/or the drying technique of the layer may be chosen in such a way that a natural adhesion occurs between the layer and the support, which optionally has been coated with a proper subbing layer(s).

When a hydrophilic continuous phase is present and this is preferred in the photosensitive recording layers applied in the present invention (a) hydrophilic polymer(s) acting as binding agen(s) are used, e.g., hydrophilic natural colloids, modified hydrophilic natural colloids, or synthetic hydrophilic olymers. MOre particularly they may be selected from such film-forming water-soluble natural or modified natural hydrophilic colloids as, e.g., gelatin, glue, casein, zein, hydroxyethyl-cellulose, carboxymethylcellulose, ethyl-cellulose, carboxymethyl-hydroxyethyl-cellulose, gum arabic, sodium alginate and hydrophilic derivatives of such colloids. They may also be selected from such synthetic hydrophilic polymers as, e.g., polyvinyl alcohol, polyvinyl-N-pyrrolidone, polyvinyl amine, polyethylene oxide, polystyrene sulphonic acid, polyacrylic acid and hydrophilic copolymers and derivatives of such polymers. The hydrophilic polymers are preferably of such a high molecular weight that they are film-forming and may be hardened to a certain extent for obtaining a higher mechanical strength. E.g., a film-forming hydrophilic binding agent such as gelatin may be hardened with formaldehyde.

Preferred hydrophilic binding agents are of proteinaceous nature and in that respect casein and gelatin are most preferred.

The ratio by weight of dispersed hydrophobic material to hydrophilic binder is one of the features that determines the photosensitivity of the recording element. The photosensitivity'of the recording layer is measured in terms of a reduction of water permeability or increase in resistance to removal of the recording layer from its support by an aqueous treatment (washoff development) of any photographically exposed area of the recording layer. It has to be noticed that in the determination of the photosensitivity the temperature of the irradiated portions of the recording layer is not raised or not substantially raised in respect of the nonirradiated portions.

It has been experimentally found that a practical useful sensitivity for reproduction of informationwise modulated electromagnetic radiation by a washoff development can be obtained with a ratio by weight of dispersed hydrophobic substance, preferably hydrophobic thermoplastic polymer particles solid at room temperature, to hydrophilic binder from at least 1:1 on. Preferably the recording layer contains from 35 to percent by weight of hydrophilic binder in respect to the finely divided hydrophobic material. Optimal results were ob tained with a ratio by weight of hydrophobic dispersed particles to hydrophilic binder of 4: 1.

According to a preferred embodiment of the present invention the photoconductive substances surround the dispersed hydrophobic particles in the recording layer.

According to a particular embodiment the aid hydrophobic particles consist of a hydrophobic photoconductive substance, e.g., poly-N-vinylcarbazole or are hydrophobic particles containing photoconductive substances, e.g., dissolved in a hydrophobic wax or polymer, or such substances in particulate form surrounded by hydrophobic material or a capsule shell.

According to a preferred embodiment a photoconductive substance, which without being heated in electromagnetically irradiated state causes the coagulation of hydrophobic dispersed material, is applied in dissolved state and in molecularly divided form surrounds the hydrophobic particles. Preferably used photoconductive substances are hydrophilic enough for being compatible (for forming a solid state solution) with a hydrophilic polymer. Thus, for example, when the hydrophilic polymer has the capability of gel-sol transformation, the photoconductive substance is dissolved in the solution from which the gel is formed and forms a solid state solution with the continuous hydrophilic binder.

The photoconductive substances may be sensitive to any type of electromagnetic radiation e.g., X-rays, ultraviolet light, visible light and/or infrared light. If they are not sensitive for visible light they can be spectrally sensitized for the part of ing agents.

Photoconductive substances that are inherently sensitive to visible light are found in the group of photoconductive organic dyes and inorganic colored photoconductive substance, e.g., cadmium sulphide, cadmium sulphide selenide and lead(ll) oxide.

Preferred organic photosensitive semiconductive compounds changing their electrical behavior on exposure to active electromagnetic radiation are found in the group of organic photoconductive dyes. Particularly those are useful that have also spectral sensitizing properties with respect to photoconductive zinc oxide. Such dyes are found in the class of: xanthene dyes preferably fluorescein dyes, thiazine dyes, and acridine dyes preferably water-soluble acridine dyes. A large number of these dyes are characterized by their fluorescence and are described e.g., in the US. Pat. No. 2,875,047 of Gerard Oster, issued Feb. 24, 1959.

For the photoconductive properties of fluorescein dyes such as eosine reference is made e.g., to Semiconductive properties of organic dyes by A. T. Vartanyan, Izvest.Akad.Nauk, S.S.S.R., Ser.Fiz. l6 1952), p. 169-185, cf. CA. 45, 3709 i).

The dyes are preferably applied in dissolved form. Preferably they are dissolved in water and added in that state to the dispersion of hydrophobic particles in a hydrophilic binder.

Depending on the type of organic photoconductive substance the ratio by weight of said substance in respect to the total amount of hydrophobic particles, preferably thermoplastic polymer particles and hydrophilic binder, can be as low as 0.05 percent. Very high sensitivity is obtained with fluoresceine dyes such as eosine and erythrosine.

According to the present invention organic photoconductive dyes are preferably used which are photoreducible dyes incapable of being reduced by a thiol polymer such as gelatin to which sulfhydryl groups were added (so-called thiolated gelatins) in the absence of light, but capable of being reduced by the sulfhydryl groups of the polymer when photoexcited with visible light. For such type of dyes reference is made to the US. Pat. No. 3,145,104 of Robert G. Carlson, issued Aug. 18, 1964. These photoreducible dyes include photoconductive members of the fluorescein class, the thiazine class, the acridine class, and the porphyrin class. Suitable photoreducible dyes are, e.g., rose bengal phloxin, erythrosin, eosin, fluorescein, acriflavin, thionin, riboflavin, chlorophylls, hematoporphyrin, proflavin and methylene blue. The dyes soluble in an aqueous medium are prefereed, viz fluorescein dyes, thiazine dyes and water-soluble acridine dyes that are preferably combined with a proteinaceous colloid forming the hydrophilic continuous phase of the recording layer.

Preferred inorganic photoconductive substances are the photoconductive compounds of inorganic type consisting of a photoconductive metal or of a photoconductive metal compound containing an element of the Group 6B of the Periodic Table.

Specific inorganic semiconductor materials having photoconductive properties and that can be used in the materials of the present invention are Ge; TiO ZnO; ZrO 2; GeO,; ln O SnO- Bi,o,; PbO; BeO; Sb O Si() BaTiO Ta O TeO B 0 ZnS; MnO SnS CdS, CdSe; CdS-Se; red lead oxide (Pb o chromium(lll)oxide These semiconductor materials can be sensitized by a number of techniques known in the art such as doping with foreign ions, dye sensitization, and heating.

Preferred members of that group are photoconductive zinc oxide, titanium(lV) oxide, lead(ll) oxide (PbO), preferably the yellow variety (massicot), red lead oxide (Pb O.,), chromium(IlI) oxide and cadmium sulphide.

The preferred type of photoconductive zinc oxide is the type used in electrophotographic recording materials, more preferably white photoconductive zinc oxide prepared by the oxidation of zinc vapor (according to the French process).

In the preparation of a recording layer suited for the production of continuous tone images lead(ll) oxide yields excellent results. There are two types of lead(ll) oxide viz the red lead(ll) oxide having a tetragonal crystal structure and the yellow lead(ll) oxide having an orthorhombic crystal structure, which is preferred in the present invention for X-ray recording.

Further good results are obtained with photoconductive titanium(lV) oxide especially with that type of titanium (IV) oxide that is useful for a recording process as described in United Kingdom Pat. No. 1,043,250 filed Apr. 23, 1963 by ltek Corp. This Patent Specification relates to a method of producing a visible image in a copy medium comprising a radiation-sensitive metal-containing semiconductor compound that becomes conductive on the impingement of radiation thereon, which method comprises exposing said medium to an image pattern of activating radiation thereby reversibly activating said semiconductor compound to render it capable of causing chemical reaction at portions of said medium corresponding to said image pattern of radiation, and then developing reversibly activated portions of said medium by contacting at least said portions with a liquid redox system reacting on contact at said reversibly activated portions to form reaction products defining a visible image corresponding to said image pattern.

Photoconductive titanium(lV) oxide particles having particularly good properties for use according to the present invention have an average particle size not greater than 250 millimicrons. Such finely divided titanium(lV) oxide is preferably produced by processes involving the pyrolysis of titanium(lV) chloride (see United Kingdom Pat. Specification No. 1,101,516 filed Apr. 14, 1965 by ltek Corp.). Titanium(lV) oxides having an average particle size between 25 and 100 millimicrons are preferred.

By average particle size is meant the particle size at the peak of the frequency distribution graph of a mixture of particles having decreasingly small numbers of larger particles and of smaller particles.

The ratios by weight of dispersed nonspectrally sensitized inorganic photoconductive substance to the total amount of hydrophobic thermoplastic polymer particles are preferably in the range of 1:3 to 5:3.

The photoconductive compounds of the inorganic type can be spectrally sensitized or doped, e.g., photoconductive zinc oxide and titanium(lV) oxide can be very advantageously spectrally sensitized by means of fluorescein dyes e.g., with eosin and erythrosin. Photoconductive lead(ll) oxide can be doped e.g., with bismuth.

Suitable inorganic colored photoconductive substances that are inherently sensitive for visible light are, e.g., photoconductive lead(ll) oxide, cadmium sulphide, cadmium selenide and mixed crystals of cadmium sulphide selenide which photoconductors optionally can be used in a mixture containing a white photoconductor, e.g., photoconductive zinc oxide.

Dispersed photoconductive substances, which on exposure to active electromagnetic radiation makes a recording layer used according to the present invention less water permeable, preferably have a grain size not substantial greater than that of the dispersed hydrophobic material. So, the grain size is preferably below 10,u., and more preferably in the range of 0.1 to 0.5a.

The amount by weight of said photoconductive substance in the recording layer is preferably high enough to obtain a practically useful image reproduction quality by a washoff development within exposure times no longer than minutes with conventional commercial copying apparatus light sources, e.g., U.V.-emitting mercury vapor tubes as are used in diazocopying machines, incandescent tungsten filament lamps such as the iodine filled tungsten filament lamps used in a Dual Spectrum (trade name) copier. For example 24 30 v./39 w. lamps are used in the exposing section of the model 76 Dual Spectrum copier.

From the following table sensitivity values as a function of layer composition can be learned. The recording layer contained percent by weight of glycerol per 100 g. of polyethylene.

The recording layers were exposed through a grey step wedge (constant 0.1) with a l500-watt quartz-iodine lamp held at a distance of 65 cm of the recording layers, which were not in thermal contact with the wedge. ln order to exclude the influence of heat possibly produced on exposure the latter was carried out on a thermostatically controlled (20 C.) vacuum frame.

Under the same circumstances all the exposed materials were subjected to a washoff development in an automatically operating washoff apparatus as described in the Belgian Pat. No. 715,932 filed May 31, 1968 by Gevaert-Agfa NV. The light energy corresponding with the first nonwashed-off step is a measure for the sensitivity.

TABLE Ingredients of the recording layer g./m.

Polyethyl- Photoeon- Sensitivity ene latex ductive particles ZnO parti- Lux. sec. Joule! 0.1;t) cles (0.17 Eosin cm.

Practical useful results are obtained with 0.3 to 1.7 parts by weight of a photoconductive substance such as photoconductive zinc oxide and 1 part by weight of thermoplastic polymer particles such as polyethylene particles.

In addition to the dispersed hydrophobic particles and/or hydrophilic binder, the photosensitive layer applied in the present invention may contain all kinds of ingredients such as non-light-sensitive pigments, plasticizing agents for the hydrophilic binder and/or for the dispersed polymers improving their sticking contact, electrically conductive particles e.g., carbon particles, dyes, e.g., dyes which can be bleached, water-soluble dyes, reaction components for the formation of dyes, catalysts for color reactions, developing nuclei, lightsensitive substances, e.g., silver halide, diazonium salts, developing substances for silver halide or complexed silver halide, finely divided metal that e.g., can be etched away, reaction components that can be distilled preferably below 80 C and other image-forming material. Further this layer may comprise hardening agents for the hydrophilic binder and optionally curing agents, which harden the hydrophobic thermoplastic polymer at elevated temperatures.

According to a preferred embodiment a photosensitive recording material according to the present invention contains substances that increase the photosensitivity without, however, enlarging the spectral sensitivity. Such substances are found in the class of hygroscopic compounds. Preferred substances are hygroscopic polyols, such as glycerin. Hygroscopic or slightly hygroscopic ionic compounds can increase the sensitivity, e.g., lithium chloride and potassium bromide.

According to their purpose the materials comprising a lightsensitive element according to this invention may be composed differently. By way of example the photosensitive layer containing the photocoaguable composition may be applied to a hydrophilic layer, which occasionally serves as a support. By hydrophilic layer is understood a layer that is wettable by water or by aqueous solutions. Such a layer may be porous or water-permeable. By way of example this hydrophilic layer may be composed mainly of natural or synthetic colloids that are soluble or dispersible in water. Examples of such layers are a gelatin layer, a light-sensitive silver halide emulsion layer, a water-permeable nuclei containing colloid layer for application of the silver complex diffusion transfer process, a barytacoating comprising gelatin and barium sulphate, a gelatin layer containing pigments or dissolved dyes, or containing reaction components capable to produce a color reaction, a

gelatin layer containing developing substances for silver halide or complexed silver halide, or a gelatin layer containing finely divided metal that can be etched away, e.g., silver.

Further, the recording layer according to the present invention can be applied between two hydrophilic layers, a hydrophilic and a hydrophobic layer, between two permeable layers, or between a permeable and an impermeable layer.

A layer or sheet being in contact or water-permeable relationship with the photosensitive layer may contain all kinds of ingredients, e.g., ingredients that can be of practical interest to the present invention. This survey is intended for illustrating the possibilities and advantages of the invention without limiting therefore the scope of this invention. According to a first system, the imagewise differentiation in permeability is utilized for applying by imagewise diffusion image-forming substance or substances in the recording element by a liquid treatment or to transfer such substances from the recording element to a receiving material respectively, said imagewise diffusion being possible as a consequence of the permeability difprovide adherence to the recording layer. In other words such 10 ferentiation. By way of example for the first system a dye difa layer may act as a subbing layer (suitable subbing layers for use in combination with recording layers of the present invention are described in the French Patent No. 1,507,874 filed .Ian. [0, 1967 by Gevaert-Agfa N.V.). Other ingredients may be of interest to develop the recorded image, e.g., pigments, dyes, reaction components for the formation of dyes, developing substances, reaction components or dyes, which can be distilled preferably below 80 C., light-sensitive substances, e.g., silver halide or diazonium salts, developing nuclei suited for use in the silver halide diffusion transfer process, catalysts for color reactions, and/or conductive particles, e.g., metal particles.

Depending on the use of the recording material the support of the recording layer may be rigid or flexible.

When flexibility is preferred a sheet element such as e.g., a paper sheet, a plastic film, a metal foil or the like is used. When flexibility is unimportant, plates of metal, glass, plastics, fiber board, cardboard or the like may be used. The support may be permeable as well as impermeable e.g., it may be water-permeable such as a wire screen or a web of textile.

Suitable water-impermeable supports are made of hydrophobic resins, e.g., of cellulose ester derivatives polyester. polystyrene, hydrophobic metal, hydrophilic metal coated with a hydrophobic layer e.g., an oxide layer, glass and the like. In order to improve the adherence of the recording layer to its support one or more subbing layers may be applied.

Recording according to the present invention can proceed in different ways according to the method in which radiation is supplied to the recording element.

It has to be noted, however, that the present invention is not based on informationwise melting or softening of dispersed hydrophobic thermoplastic particles in the recording layer and consequently no informationwise heat absorption in the recording layer has to taken place. I

A short-duration high-intensity electromagnetic exposure producing a substantial internal heating of the recording layer is not within the scope of the present invention, about this reference is made to the Canadian Pat. No. 806,124 of Gevaert-Agfa N.V., issued Feb. I l, 1969. Taking into account the sensitivity of up till now manufactured recording layers exposures lasting longer than 10" sec. using continuously operating (no flash lamps) common copying apparatus radiation sources are applied.

According to one embodiment, a transparent original hearing light-absorbing indicia is recorded by bringing the photosensitive element of a recording material according to the present invention into contact with said original, and exposing said photosensitive element while in contact to electromagnetic radiation of such intensity and for such a time as to record the image in terms of water permeability differences without a substantial increase in temperature of the portions of said element corresponding to the transparent portions of the original.

According to another embodiment an opaque or transparent original is projected onto the recording material (episcopically or diascopically projection). Thus, the present invention provides the possibility to make enlarged photographs by projection exposure.

Before giving some examples for practising the method of the present invention, a short survey is given of different systems that are suited for the manufacture of copies and masters for the reproduction of originals starting from an electromagnetic-radiation-imaged recording material according to fuses inthe recording element (layer or sheet) only on the areas that remain permeable and sufficiently hydrophilic. Of course, instead of a dye solution, a solution of a catalyst for initiating a color reaction between components in the recording material or a solution of a colorless reaction component capable of giving a color reaction with a colorless or slightly colored reaction component in the recording material can be used.

By way of another example for the first system it is possible to incorporate into the recording element colored substances which can be bleached out by a bleaching agent diffusing in the areas of the recording material that remained permeable. According to an alternative of that system, a conductive substance, e.g., a metal that can be etched away such as colloidal silver, and that is homogeneously dispersed in the recording element, is imagewise etched away by an etching liquid diffusing into the permeable areas. The photosensitive layer can be applied to an etchable base material, e.g., a resin sheet coated with aluminum. When using this material it is possible by imagewise etching to produce a planographic letter-type or in taglio printing master.

In a method embodiment of image formation wherein diffusion is applied, the image-forming substance incorporated into the recording material is transferred by diffusion from the areas that remain permeable to an image-receiving material. 50, it is possible, e.g., to incorporate a soluble dye into the recording element or into a layer being in a liquid-permeable 0 relationship therewith, said dye being capable of diffusing therefrom imagewise to a receiving material when the photographically exposed recording element is wetted.

Self-evidently, instead of a dye a colorless reaction component or catalyst for the formation of a color reaction with a reaction component in the receiving material can be incorporated into the recording element.

So, it is Imagewise possible to incorporate into the recording material silver salts that can be complexated and that in their dissolved form can diffuse to a receiving material containing reduction nuclei or development nuclei, whereupon according to the areas of the recording material that remained permeable, silver is deposited imagewise.

In these diffusion methods the image-forming substances such as a dye, a metal that can be etched away, or reaction components need not be present in the recording element itself; they can also be incorporated into a layer or support being in a water-permeable relationship therewith.

According to a second system the portions of the informationwise electromagnetically irradiated recording material that remained sufficiently water-permeable are eliminated e.g., by washing out or degrading of the hydrophilic binder, and by removing the hydrophobic particles that were not coagulated by exposure. By that technique a direct visible copy of the information is obtained when the recording element comprises a dye, e.g., a (colored) pigment and/or a dissolved dyestuff before exposure.

By applying said second system, a gravure master can be produced by starting from the imaged recording layer, which is applied to a metal support that can be etched. After elimination of the portions of the recording layer that remained permeable and hydrophilic, e.g., by washing out and after making the portions of the recording layer left sufficiently resistant to the etching solution the uncovered metal can be etched away imagewise. In this way e.g., printed circuits can be produced. After the elimination, e.g., by means of an organic solvent, of the portions of the recording layer left after i the washoff development, the etched metal plate according to the depth and manner of etching can be used as a planographic printing master, a gravure master or a letterpress master.

By applying said second system also a stencil or screenprinting master can be manufactured by starting from an informationwise electromagnetically irradiated recording material according to the invention. For this technique either one or both sides of a screen material are coated with a recording layer, or the screening material makes part of a selfsupporting sheet as described hereinbefore. As screen material Japan paper (Yoshino paper), nylon fabrics with a size of mesh of 0.2 to 0.08 mm. and woven bronze wire are especially suited.

For the screen-printing technique it is known that only on the open (permeable) areas of the fabric (screen material) ink can pass and deposit on the material to be printed corresponding to these areas. The imagewise open areas are obtained according to the present invention by washing out or degrading the recording layer composition in the areas where this layer or sheet remained permeable and hydrophilic.

According to a third system the image portions that remained permeable and hydrophilic are transferred onto a receiving material by squeegeeing and tearing out.

This type of transfer is possible if the cohesion of the matter of the receiving material is larger than that of the matter in the permeable portions of the recording layer, and if the adhesion between said permeable portions and the receiving material is larger than the cohesion of the matter of said permeable areas.

This transfer successfully occurs when separating after pressing together a wetted informationwise electromagneti cally irradiated recording element according to the present invention from a receiving material preferably having a hydrophilic and/orporous surface, e.g., a paper sheet. In that embodiment the recording layer preferably comprises a hydrophilic binder wherein hydrophobic thermoplastic polymer particles are dispersed.

The contrary type of transfer is possible if the cohesion of the matter of the receiving material is less than that of the matter in the permeable portions of the recording layer, and if the adhesion between said permeable portions and the receiving material is larger than that of the matter of said receiving material. E.g. a dye layer of a carbon paper being little hydrophobic on its surface, such as is used in the process according to the French Pat. No. 1,466,223 filed July 30, 1963 by Gevaert Photo-Producten N.V., after being pressed onto the moistened heator pressure-imaged material, can be transferred imagewise to the permeable and hydrophilic areas of the recording material on separating it therefrom. Before pressing the recording layer into contact with the dye layer, the hydrophilic binder of the recording layer can be swollen so that a relief image is formed that makes possible a closer contact with the dye layer.

According to this third system it is thus possible to manufacture hectographic masters since the pulled out material can contain a hectographic dye that is soluble in the transfer liquid or can contain a reaction component forming a dye with a reaction component present, e.g., in the transfer liquid or transfer material.

According to a fourth system it is possible by using a low melting dye in the recording element, to transfer this dye by heating the imagewise washed-off recording element in contact with a transfer material.

The following examples illustrate the invention.

The percent ratios are by weight if not otherwise indicated.

EXAMPLE] A poly(ethylene terephthalate) support of mm.

thickness was coated with the following composition in a proportion of 18 g./sq.m.:

20% aqueous dispersion of co(viny1idene chloride/ntert.-buty1 acrylamide/itaconic acid) (molar ratio 88/ 10/2) 12 g. 40% aqueous dispersion of polyethylene having a particle size less than 0.1;1. and an average molecular weight comprised between 15,000 and 30,000 12 g. 30% aqueous dispersion of colloidal silica 12 g. ethyl alcohol g.

water 864 g.

This subbing layer was dried at 30 C. On this layer a lightsensitive layer from the following composition was coated in a proportion of 50 g./sq.m.:

10% aqueous gelatin solution (Bloom gel strength number: 260 200 g. 40% aqueous dispersion of colloidal polyethylene having a particle size less than 0.1;:- and an average molecular weight comprised between 15,000 and 30,000 200g. 50% aqueous dispersion of photoconductive zinc oxide (average particle size 0.17;) 320 g. glycerol 15g. ethyl alcohol 90 g.

water g.

The light-sensitive layer was dried at 25 C.

The light-sensitive material thus obtained was vacuum-contact exposed for 10 minutes through a developed silver halide emulsion layer containing a negative screen print by using a 1,500-watt quartz-iodine lamp mounted in a reflector at a distance of 30 cm. above the vacuum frame.

After exposure the material was rubbed with a soft sponge whilst abundantly moistening with water of 20 C. The nonexposed parts were thus whiped off and a relief image was obtained.

Instead of using plain water a 5 percent solution of potassium thiocyanate or sodium salicylate may be used.

When in the composition of the light-sensitive layer the gelatin was replaced by polyvinylpyrrolidone, analogous results were obtained although the differentiation in solubility between exposed and nonexposed parts was not as high as when gelatin was used.

EXAMPLE 2 A poly( ethylene terephthalate) support of 0.1 mm. thickness provided with a subbing layer for gelatin was coated with the following composition at a rate of 30 g./sq.m.:

10 '70 aqueous gelatin solution 400 g. 40 aqueous dispersion of polyethylene having a particle size of less than 0.1p. and an average molecular weight comprised between 15,000 and 30,000 320 g. 10% aqueous saponine 40 g. 3% aqueous solution ofthe sodium salt of the condensation product of oleic acid and methyl taurine 40 g. 4% aqueous formaldehyde 20 g.

The interlayer was dried at 30 C. On this layer a light-sensitive layer was coated at a rate of 50 g./sq.m. from the following composition:

10% aqueous gelatin solution 138 g. 40% aqueous dispersion of polyethylene having a particle size ofless than 0.1 and an average molecular weight comprised between 15,000 and 30,000 138 g. 10% aqueous dispersion of colloidal silver 250 g. 50% aqueous photoconductive zinc oxide dispersion (average particle size 0.17p.) 220 g. ethyl alcohol 90 g.

This layer was dried at 25 C.

The material was exposed in a diazo printer Buroza 600 sold by Atlas, Delft, Holland, at a setting 3, through a developed silver halide emulsion layer containing a negative halftone print. I

After exposure the material was dipped in a conventional bleaching bath. Only the areas corresponding with the nontransparent parts of the original were bleached out so that a positive print of the photographic negative was obtained.

EXAMPLE 3 On a poly(ethylene terephthalate) support provided with the same subbing layer as described in example I was coated a light-sensitive layer from the following composition at a rate The light-sensitive layer was dried at C.

On this layer a line-image was projected by making use of a conventional transparency projector with a 250-watt lamp positioned on 1 meter distance from the light-sensitive material and giving a tenfold linear enlargement of the original. After an exposure time of 90 minutes the material was treated as in example 1, and a positive enlarged image of the original was obtained. The same material was contact-exposed for 3 minutes through a developed silver halide negative halftone print by making use of a carbon arc working at 60 a. and 3X42 v. (three phase-current) The diameter of the carbon rods was 20 mm., producing a stable arc of 4 kw. power and placed at a 4 distance of 1 meter. After exposure the material was treated as described in example 1 and a positive image of the original was obtained. The same material was contact-exposed for 10 minutes by using a 900-watt mercury vapor lamp placed at a distance of 25 cm. After exposure it was treated as the foregoin g one and a same result was obtained. This last exposure was carried out in a vacuum frame wherein the light-sensitive material was cooled on a hollow metal plate having cold water 15 C.) streaming through.

EXAMPLE 4 To a paper support coated with polyethylene and weighing 120 g./sq.m. a subbing layer was applied from the following composition at a rate of 30 g./sq.m.:

This layer was dried at 25 C. On this layer a heat-sensitive layer was coated at a rate of 40 g./sq.m. from the following composition:

. 7O 10% aqueous gelatin solution 200 g. 40% aqueous dispersion of polyethylene (see example I 200 g.

50% aqueous photoconductive xide dispersion (average glycerol particle size 017 300 g. glycerol 15 g. ethyl alcohol g. l6% aqueous dispersion of carbon (average particle diameter 0.11.1) with 2% poly-N-vinylpyrrolidone 50 g.

This layer was dried at 25 C., exposed and treated as in example l. A positive image of the silver halide original was obtained.

EXAMPLE 5 A poly(ethylene terephthalate) base of thickness 0.1 mm. provided with a subbing layer described in example 1 was coated with the following composition at a rate of 50 g./sq.m.:

10% aqueous solution ofgelatin 200 g. 40% aqueous dispersion of polymethyl methacrylate particles sizing on the average 0.12;. and having an average molecular weight of 1,300,000 200 g. 50% aqueous dispersion of photoconductive zinc oxide (average particle size 0.l7;.i) 320 g. glycerol 15 g. ethyl alcohol 90 g.

This coating was dried at 30 C.

Exposure and development were done as described in example l and analogous results were obtained.

Same results were obtained when the 200 g. polymethyl methacrylate were replaced by 374 g. of a 22 percent dispersion of polystyrene with an average particle size 0.13u and an average molecular weight 50,000. I

EXAMPLE 6 A poly(ethylene terephthalate) base of thickness 0.1 mm. provided with a matted layer consisting mainly of an urea formaldehyde resin and crystalline silica was coated with a subbing layer of the following composition at a rate of 15 g./sq.m.:

aqueous polyethylene dispersion (as described in example 1 19 g. aqueous dispersion of a copolymer of butadiene and methyl methacrylate (SO/50) 20 g. 10% aqueous colloidal dispersion of silica 50 g. ethyl alcohol 50 g. water 361 g.

This layer was dried at 35 C. Onto the layer a photosensitive layer was coated at a rate of 50 g./sq.m. from the following composition:

l0% aqueous solution of gelatin mixture of aqueous dispersion of colored pigments: 4 parts of Permanent Gelb HR Colanyl Teig (a yellow pigment insoluble in water,

sold by Farbwerke Hoechst AG,

Frankfurt (M)-Hochst, West Germany), 20 parts of Permanent Carmin FEB Colanyl Teig (a magenta pigment insoluble in water, sold by Farbwerke Hoechst AG) and 26 parts of Heliogengrun CN Colanyl Teig (a green pigment insoluble in water, sold by Farbwerke Hoechst AG 50% aqueous dispersion of photoconductive zinc oxide (average particle size 0. l5;:.) 20% aqueous dispersion of polyethylene prepared as described hereinafter ethyl alcohol 400 g. 90 g. is g.

The material thus obtained was exposed for 5 minutes through a developed silver halide emulsion layer containing a negative silver print by using a l,500-watt quartz-iodine lamp, placed at a distance of 30 cm.

After exposure the material was treated as described in example and a sharp positive print was obtained.

Same results were obtained when the photosensitive composition was qae taarti mmma Preparation of the latex in a 4,000 cc. steel pressure tube were placed a partly oxidized polyethylene prepared according to United Kingdom Patent 997.135

filed Oct. 25. I963 by Grace & Co.,

W.R. having the following characteristics:

average molecular weight:

7,000-crystalline melting point:

l2S-l 30 C.acid number: 26-30 40 g. n-hexadecyloxydecaoxyethylene 12.4 g. water I50 g.

The pressure tube was sealed and rotated at 30-40 r.p.m. at l90-200 C. for 1 hour in order to disperse the mixture. Then the tube was allowed to cool slowly to room temperature. The obtained dispersion was ready for use as such.

EXAMPLE 7 A transparent non-heat-conductive poly(ethylene terephthalate) support of 0.1 mm. thickness was provided with a subbing layer of the following composition at a rate of 18 g./sq.m.:

20% aqueous dispersion of copolymer of vinylideneehloride, N-tert. butylacrylamide and itaconic acid (molar ratio 88/10/2) 40% aqueous dispersion of polyethylene having a particle size of less than 0.1;. and an average molecular weight comprised between l5.000 and 30,000

30% aqueous dispersion of colloidal silica ethyl alcohol water l2 g. I00 g. 864 g.

This subbing layer was dried at 30 C. To this subbing layer a light-sensitive layer was applied from the following composition at a rate of g./sq.m.:

a partly oxidized polyethylene prepared according to United Kingdom Patent 997,115 mentioned above,

by the oxidation of polyethylene [average molecular weight: 7,00() crystalline melting point: l25-l30 C. acid number: 26-30) n-hexadecyloxy decaoxyetliylene water 40 g. l2.4 g. I50 g.

The pressure tube was sealed and rotated at 30-40 rpm. at l-200 C. for l hour in order to disperse the mixture. Then the tube was allowed to cool slowly to room temperature. The obtained dispersion was ready for use as such. 75

EXAMPLE 8 On the light-sensitive material described in example 7, a negative line transparency was projected by means of a conventional projector with a 250-watt lamp positioned at l meter from the light-sensitive layer and enlarging the original tenfold. After an exposure time of 10 minutes the material was treated as described in example 7. A positive enlarged copy of the transparency was obtained.

EXAMPLE 9 The light-sensitive material as described in example 7 was placed with its light-sensitive layer into contact with the printed side of a graphic original on a paper base.

The material was exposed for 2 minutes through its transparent support in a flat contact-exposure apparatus containing 8 white fluorescent light tubes of 200 watt each placed under a glass plate of 45 cm. X 65 cm. and yielding a 20,000 lux light output.

After exposure, the material was rubbed with a soft sponge wetted with water of 35 C. The parts of the light-sensitive material corresponding with the image parts of the original were washed off. A negative copy of the original was obtained.

EXAMPLE 10 A poly(ethylene terephthalate) support of 0.1 mm. thickness provided with a subbing layer described in example 7 was coated with the following composition at a rate of 60 g./sq.m.:

l0% aqueous solution of gelatin 20% aqueous dispersion of polyethylene prepared as described in example 7 50 g. glycerol 5 g. aqueous dispersion of carbon black containing 36 g. of carbon black (average particle size: 0.lp.).

23 g. of water, 30 g. of ethylene glycol and 6 g. of nonylphenyl (diethylene oxide) 9-l0 water lead(ll) oxide (yellow type) powder doped with 30 p.p.m. of bismuth (specific surface: L56 sq.m./g.

The lead(ll) oxide powder was dispersed with vigorous stirring. The coating was dried at 30 C.

The light-sensitive material thus obtained was vacuum-con- 0 tact exposed for 10 minutes through a developed silver halide emulsion layer containing a negative halftone print by means of a 1,500-watt quartz-iodine lamp mounted in a reflector at a distance of 30 cm. above the vacuum frame.

After exposure, the material was rubbed with a soft sponge abundantly moistened with water of 20 C. so that the nonexposed parts were whiped off. A sharp black positive relief image was obtained.

Analogous results were obtained by replacing lead(lI) oxide by a same amount of cadmium sulphide powder, red lead oxide pb oo powder, mercury(ll) oxide powder, manganese(IV) oxide powder or chrominumflll) oxide powder. The average particle size of the powder particles was between 1 and 5 u.

EXAMPLE 1 l A poly(ethylene terephthalate) support of 0.1 mm. thickness provided with a subbing layer as described in example 7 was coated with the following composition at a rate of 45 g./sq.m.:

I096 aqueous solution of gelatin 200 g. 20% aqueous dispersion of polyethylene (prepared as descri ed in example 7) I50 g.

cosine 0.25 glycerol 8 g. aqueous solution of isononylphenyl decaethoxanol g.

water 72 g.

amount of Acridine Orange R known as Basic Orange 14 (CI. 46,005)

On a subbed cellulose triacetate support were coated the following dispersions containing respectively:

Composition A B O D Dernineralised water, cc 60 60 60 60 2 2 2 2 2 2 60 40 20 40% aqueous dispersion of polyethylene having a particle size of 0.111 and an average molecular weight of 30,000, cc 20 40 60 80 Glycerol, g 6 6 6 6 1 1 1 1 These compositions were coated at such a rate that after drying recording layers of 40 p. thickness were obtained.

The recording materials were now laid with their supports onto a transparent line original and exposed through the latter for 30 minutes by means of a Philips HPR 125 lamp placed at a distance of 30 cm. Thereupon the exposed light-sensitive layers were treated with water of 35 C. resulting in the removal of the nonexposed portions of the recording layers.

The sensitivity of the recording layers formed with said compositions A, B, C and D respectively was in the following EXAMPLE 13 Example 12 was repeated with the difference, however, that in the recording layer the 2 g. of eosine were replaced by 12 g. of yellow lead(ll) oxide and the sodium hexametaphosphate and the lead(ll) oxide were ball-milled in demineralized water, for 1 hour, before the other ingredients were added.

After imagewise exposure for 5' minutes by means of a Philips HPR 125 lamp and a treatment with water of 35 C., only the nonexposed portions of the different recording layers were removed. i

The sensitivity of the recording layers formed with said compositions A, B, C and D respectively was in the following order: A B C D.

EXAMPLE l4 with a subbing layer of the following composition at a rate of 18 g./sq .m.:

20% aqueous dispersion of copolymer of vinylidene chloride, N-tert.-butyl acrylamide and itaconic acid (molar ratio 88/l0/2) 12 g. 40% aqueous dispersion of polyethylene having a particle size ofless than 0.1;

and an average molecular weight comprised between 15,000 and 30.000 l2 g. 30% aqueous dispersion of colloidal silica l2 g. ethyl alcohol I00 g. water 864 g.

This subbing layer was dried at 30 C. To this subbing layer a light-sensitive layer was applied from the following composition at a rate of g./sq.m.:

l0% aqueous solution of gelatin 20% aqueous dispersion of polyethylene prepared as described hereinafter 50% aqueous dispersion of photoconductive zinc oxide prepared by the oxidation of zinc vapor (the zinc oxide grains have an average particle size of 017p) glycerol 5% aqueous solution of isooctylphenyl-poly(ethylene oxide (n=9) carbon black dispersion containing 36 g. of carbon black, 23 g. ofwater,

30 gv of ethylene glycol and 6 g. of nonylphenyl-poly(ethylene oxide lOO g.

IOg.

log.

. tact with the polyethylene terephthalate support of the lightsensitive layer.

After exposure the light-sensitive layer was gently rubbed with a soft sponge while being wetted abundantly with water of 50 C.

A positive continuous tone copy of the original was ob tained.

Preparation of the polyethylene latex In a 4,000 cc. steel pressure tube were placed:

a partly oxidized polyethylene prepared according to United Kingdom Patent 997,135 mentioned above. by the oxidation of polyethylene (average molecular weight: 7,000- crystalline melting point: l25l 30 C.- acid number: 26-30) n-hexadecyloxy decaoxyethylene water 40 g. IZA g. I50 g.

The pressure tube was sealed and rotated at 30-40 rpm. at 200 C. for 1 hour in order to disperse the mixture. Then the tube was allowed to cool slowly to room temperature. The obtained dispersion was ready for use as such.

EXAMPLE 15 1013f? aqueous solution of gelatin I00 g.

T X Cqntin a 20% aqueous dispersion of polyethylene prepared as described in example 14 50 g 50% aqueous dispersion of photoconductive zinc oxide prepared by oxidation of zinc vapor and having an average particle size of 0. l 71,1 13 g. glycerol 4 g. eosine 0.5 g. water 233 g.

The coating was dried at 45 C. The material thus obtained was contact-exposed for one minute through a developed photographic silver halide emulsion layer containing a negative halftone silver image on a transparent cellulose triacetate support. For exposing a 500-watt incandescent lamp was used placed at a distance of 30 cm.

After exposure the material was treated as described in example 14. A sharp positive print was obtained.

EXAMPLE 16 On the light-sensitive material described in example 15, a line transparency was projected by means of a conventional ,projector with a 250-watt lamp positioned at 1 meter from the light-sensitive layer and enlarging the original tenfold. After an exposure time of 10 minutes the material was treated as described in example 14. A positive enlarged copy of the transparency was obtained.

EXAMPLE 17 The light-sensitive material as described in example 15 with its light-sensitive layer was placed into contact with the printed side of a graphic original on a paper base.

The material was exposed for 2 minutes through its rear side EXAMPLE 18 A poly(ethylene terephthalate) support of 0.1 mm. thickness was provided with a subbing layer of the following composition in a proportion of 18 g./sq.m.:

20% aqueous dispersion of copolymer of vinylidene chloride, N-tert.-butyl acrylamide and itaconic acid (molar ratio 88/10/2) l2 g. 40% aqueous dispersion of polyethylene having a particle size of less than 0.1 and an average molecular weight comprised between l5,000 and 30,000 12 g. 30% aqueous dispersion of colloidal silica 12 g. ethyl alcohol I g. water 864 g.

This subbing layer was dried at 30 C. To this subbing layer a light-sensitive layer of the following composition was applied in a proportion of 40 g./sq.m.:

20% aqueous dispersion of polyethylene prepared as described hereinafter 50'! nqucttun dlnpcntiun of photoeonductlve zinc oxide prepared by the oxidation of zinc vupor (the zinc oxide gruins have an average particle size of O.l7p.)

aqueous dispersion of carbon black containing 36 g. ofcarbon, 23 g. of water, 30 g. of ethylene glycol and 6 g. of nonylphenylpoly(ethylene oxide),,(n=9) glycerol water The coating was dried at 35 C. y

The light-sensitive material thus obtained was vacuum contact exposed for minutes through a developed silver halide emulsion layer containing a negative screen print by using a 5 1,500-watt quartz-iodine lamp mounted in a reflector at a distance of 30 cm. above the vacuum frame.

After exposure the material was rubbed with a soft sponge while it was kept moist with water of 20 C. The nonexposed parts were thus wiped off and a black relief image was oblO tained.

Preparation of the Polyethylene Latex In a 4,000 cc. steel pressure tube were placed:

a partly oxidized polyethylene prepared according to United Kingdom Patent 997,135 mentioned above (average molecular weight: 7,000-

crystalline melting point: l25l 30 C.-

acid number: 26-30) 40 g. n-hexadecyloxydecaoxyethylene 12.4 g. water I50 g.

The pressure tube was sealed and rotated at 3040 r.p.m. at l90-200 C. for 1 hour in order to disperse the mixture. Then the tube was allowed to cool slowly to room temperature. The

obtained dispersion was ready for use as such.

EXAMPLE l9 Subbed cellulose triacetate base strips of 0.1 mm. thickness were separately coated with one of the following compositions pro rata of 50 g./sq.m.:

The amounts by weight are in grams.

10% aqueous solution Polymer of caseine adjusted dispersion to pH9 with Na CO, A Water A1 340 85 0 A2 250 125 7 A3 170 I70 42 A4 100 200 82 A5 70 215 97 A6 50 225 I07 Polymer dispersion B 45 1 B2 250 125 7 B3 170 170 42 B4 100 200 82 BS 70 215 97 B6 225 107 Polymer dispersion 50 C C] 340 85 0 C2 250 125 7 C3 170 170 42 C4 100 200 82 C5 70 215 97 C6 50 225 107 Polymer dispersion A is a 20 percent colloidal dispersion of polyethylene having a particle size less than 0.1 and an average molecular weight comprised between 15,000 and 30,000 and made by emulsion polymerization.

Polymer dispersion B is a 20 percent colloidal dispersion of a polyethylene prepared as follows: in a 4,000 cc. steel pressure tube were placed a mixture containing a partly oxidized polyethylene mass prepared according to a method described in the United Kingdom Pat. No. 997,135 mentioned above by the oxidation of polyethylene together with a dispersing agent and having the following composition:

polyethylene (average molecular weight 7,000-crystalline melting point l25l30 C.-acid number 26-30) 40 g.

n-hexadecyldecaoxyethylene l2.4 g. water 150 g.

The presst re tube was sealed androtated at 30-40 rpm. at

l90-200 C. for 1 hour in order to disperse the polyethylene. Then the tube was allowed to cool slowly to room temperature and the obtained dispersion was ready for use as such.

Polymer dispersion C is a 40 percent by weight aqueous dispersion of polymethylmethacrylate sold under the name Neocryl A 400 by Polyvinyl Chem. Inc., Wilmington, Mass., U.S.A. which dispersion was diluted to 20 percent by weight solid content.

To each of the compositions A 1, A2, etc. 4 g. of glycerol, 4 g. of potassium bromide and 100 g. of a 0.25 percent aqueous solution of erythrosine was added.

The light-sensitive layers were dried at 25 C.

The light-sensitive material thus obtained was vacuum-contact exposed through a developed silver halide emulsion layer containing a negative halftone print using a 1,500-watt quartziodine lamp mounted at a distance of 65 cm. above the vacuum frame and supplying 24,000 lux on the recording layer involved.

After exposure the respective recording layers were rubbed with a soft sponge while abundantly moistening with water of 20 C. The unexposed or underexposed parts are thus wiped off and a relief image was obtained.

The following table represents the energy required for ob; taining image differentiation in each of the recording layers.

, @XAMPLE 20 H .r- Lux. sec. 10

A ))100 29 11.5 2. 90 3.00 B ))100 45 1. 0. 43 0. 36 0. 43 C ))l ))l00 11. 3. 60 4. 55 2. 88

The layer was dried at 20 C., exposed as described in example l and developed by a washofi treatment. Practical useful results were obtained. The dispersion of dibutylphthalate was prepared by mixing for 10 minutes in an Ultra-Turrax mixer sold by Janke & Kunkel K.G., West Germany at a speed of 6,000 r.p.m.:

dibutylphthalate 40 g. water 160 g. isooctylphenyl poly(ethylene oxide),' 3 g. nonylphenyl poly(ethylene Same results were obtained when the dibutylphthalate was replaced by paraffin oil or camauba wax.

EXAMPLE 21 A Japan paper weighing 14 g./sq.m. was soaked with a dispersion consisting of:

l()% aqueous solution of caseine 100 g. aqueous polymer dispersion B of Example 19 200 g. glycerol 4 g. polunsium bromide 4 g. 0.25% aqueous solution of crythrosinc 100 g.

Upon drying this Japan paper comprised 12 g. solid substance per sq.m. The thus treated paper was contact exposed for 5 minutes through a developed silver halide emulsion containing a positive line-image with a quartz-iodine lamp of M Placed a a di tsqsqsfiemrw After exposure the paper was dipped in water of 20 C. while being rubbed with a soft sponge. By this treatment the nonexposed parts were washed away and after drying a positive stencil master of the original was obtained.

We claim:

1. A method of recording information comprising 1. lmagewise exposing to active electromagnetic radiation a recording material including a water-permeable recording layer consisting essentially of a continuous phase of a film-forming hydrophilic colloid binder having uniformly distributed therethrough finely divided particles of a hydrophobic oil, wax, or thermoplastic polymer together with finely divided particles of an inorganic photoconductive compound, said binder being present in a ratio by weight of about 1:1 to 1:10 and said inorganic photoconductive compound being present in a ratio by weight of about 1:3 to 5:3 both relative to the hydrophobic particles, said exposure being for an intensity and duration sufficient to render said layer substantially impermeable to water in the exposed regions thereof while said unexposedregions remain permeable but insufficient to produce a substantial increase in the temperature of said recording layer, and

layer with an aqueous liquid to produce a visible change by penetration of or removal by such liquid of the unexposed regions of said layer, said inorganic photoconductive compound being photoconductive zinc oxide, titanium( IV) oxide, lead(ll) oxide, red lead oxide (Pb O chromium(lll) oxide, cadmium sulfide or cadmium sulfide selenide, or cadmium selenide.

2. A method according to claim 1, wherein said hydrophobic particles substantially consist of a hydrophobic thermoplastic polymer solid at room temperature.

3. The method of claim 2 wherein said thermoplastic polymer has a molecular weight of about 5,000-1 ,000,000.

4. The method of claim 1 wherein the particles of said inorganic photoconductive compound having a grain size not greater than about 10 5. The method of c arm 1 wherein said recording layer contains a water-attracting polyol or hygroscopic ionic compound.

6. A method according to claim 1, wherein said hydrophobic particles are substantially composed of at least one hydrophobic thermoplastic compound solid at room temperature.

7. A method according to claim 1, wherein said hydrophobic particles are dispersed in said continuous phase by a dispersing agent for aqueous media.

8. A method according to claim 2, wherein the polymer particles are latex particles.

9. A method according to claim 1, wherein the hydrophilic binder consists of at least one proteinaceous binding agent.

10. A method of recording information comprising 1. Imagewise exposing to active electromagnetic radiation a recording material including a water-permeable recording layer consisting essentially of a continuous phase of a film-forming hydrophilic colloid binder having uniformly distributed therethrough finely divided particles of a hydrophobic oil, wax, or thermoplastic polymer together with a water-soluble organic photoconductive xanthene, thiazine, acridine or porphyrin dye dissolved in said continuous phase, said binder being present in a ratio by weight of about 1:1 to 1:10 and said photoconductive dye being present in an amount by weight of at least about 0.05 percent both relative to the hydrophobic particles, said exposure being for a time and to radiation of a type and intensity sufficient to render said layer substantially impermeable to water in the exposed regions thereof while said unexposed regions remain permeable but insufficient to produce a substantial increase in the temperature of said recording layer, and Developing the exposed recording layer by contacting the layer with an aqueous liquid to produce a visible change i by penetration of or removal by such liquid of the unex- Developing the exposed recording layer by contacting themetal particles, dyes, and dye-forming compounds.

15. A method according to claim 10, wherein the recording layer contains a water-attracting polyol or hygroscopic ionic compound.

16. A method according to claim 10, wherein the exposed recording layer is treated with an aqueous solution of a dyestuff or, a dye-forming component.

17. A method according to claim 10, wherein the recording layer contains particles of a metal and after exposure is treated with a solution of an etching agent for said metal. 

2. Developing the exposed recording layer by contacting the layer with an aqueous liquid to produce a visible change by penetration of or removal by such liquid of the unexposed regions of said layer, said inorganic photoconductive compound being photoconductive zinc oxide, titanium(IV) oxide, lead(II) oxide, red lead oxide (Pb3O4), chromium(III) oxide, cadmium sulfide or cadmium sulfide selenide, or cadmium selenide.
 2. A method according to claim 1, wherein said hydrophobic particles substantially consist of a hydrophobic thermoplastic polymer solid at room temperature.
 2. Developing the exposed recording layer by contacting the layer with an aqueous liquid to produce a visible change by penetration of or removal by such liquid of the unexposed regions of said layer.
 3. The method of claim 2 wherein said thermoplastic polymer has a molecular weight of about 5,000-1,000,000.
 4. The method of claim 1 wherein the particles of said inorganic photoconductive compound having a grain size not greater than about 10 Mu .
 5. The method of claim 1 wherein said recording layer contains a water-attracting polyol or hygroscopic ionic compound.
 6. A method according to claim 1, wherein said hydrophobic particles are substantially composed of at least one hydrophobic thermoplastic compound solid at room temperature.
 7. A method according to claim 1, wherein said hydrophobic particles are dispersed in said continuous phase by a dispersing agent for aqueous media.
 8. A method according to claim 2, wherein the polymer particles are latex particles.
 9. A method according to claim 1, wherein the hydrophilic binder consists of at least one proteinaceous binding agent.
 10. A method of recording information comprising
 11. A method according to claim 10, wherein the said organic photoconductive dye has spectral sensitizing properties with respect to photoconductive zinc oxide.
 12. A method according to claim 10, wherein the organic photoconductive dye is a photoreducible dye.
 13. A method according to claim 12, wherein as photoreducible dye a fluorescein dye is used.
 14. A method according to claim 10, wherein the recording layer and/or an adjacent water-permeable layer contains a substance selected from the group consisting of pigments, metal particles, dyes, and dye-forming compounds.
 15. A method according to claim 10, wherein the recording layer contains a water-atTracting polyol or hygroscopic ionic compound.
 16. A method according to claim 10, wherein the exposed recording layer is treated with an aqueous solution of a dyestuff or, a dye-forming component.
 17. A method according to claim 10, wherein the recording layer contains particles of a metal and after exposure is treated with a solution of an etching agent for said metal. 